Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, 999077, Hong Kong (SAR), China.
SUSTech Energy Institute for Carbon Neutrality, Department of Mechanical and Energy Engineering, Southern University of Science and Technology, Shenzhen, 518055, P. R. China.
Angew Chem Int Ed Engl. 2023 Jul 17;62(29):e202304486. doi: 10.1002/anie.202304486. Epub 2023 Jun 12.
Non-covalent interactions play an essential role in directing the self-assembly of hybrid organic-inorganic crystals. In hybrid halide perovskites, hydrogen bonding has been the paramount non-covalent interaction. Here, we show another non-covalent interaction, namely, the halogen bond interaction, that directs a symmetry-breaking assembly in a new series of two-dimensional (2D) perovskites (ICH CH NH ) (CH NH ) Pb I (n is the layer thickness, n=1-4). Structural analysis shows that the halogen bond strength varies with the layer thickness. For the odd number (n=1, 3) layered perovskites, stronger halogen interaction leads to centrosymmetric structures, whereas for the n=2 layered perovskites, weaker halogen bonds result in non-centrosymmetric structures. Transient reflection spectroscopy shows a suppressed radiative recombination rate (k ≈0) and prolonged spin lifetime for n=2 structure, suggesting an enhanced Rashba band splitting effect. The structural asymmetry is further confirmed with a reversible bulk photovoltaic effect. Our work provides a new design strategy to enable hybrid perovskites with emerging properties and functionalities associated with structural asymmetry.
非共价相互作用在指导杂化有机-无机晶体的自组装中起着至关重要的作用。在杂卤化钙钛矿中，氢键是最重要的非共价相互作用。在这里，我们展示了另一种非共价相互作用，即卤键相互作用，它指导了一系列新的二维（2D）钙钛矿（ICHCHNH）（CHNH）PbI（n 是层厚，n=1-4）的对称性破缺组装。结构分析表明，卤键强度随层厚而变化。对于奇数（n=1，3）层状钙钛矿，较强的卤键相互作用导致中心对称结构，而对于 n=2 层状钙钛矿，较弱的卤键导致非中心对称结构。瞬态反射光谱显示 n=2 结构的辐射复合率（k ≈0）降低和自旋寿命延长，表明增强了拉什巴能带分裂效应。结构不对称性进一步通过可逆体光伏效应得到证实。我们的工作为具有新兴性质和与结构不对称相关功能的杂化钙钛矿提供了一种新的设计策略。
